Pressure regulating device



1, 1953 7 H MACK: 2,650,605

PRESSURE REGULATING DEVICE Filed Nov. 8 1948 2 Sheets-Sheet 1 '14 35 10' 16 19 a; 35 7 /6 if Y 2,? 20

L 52/ i I r .9 1/ p 6 i A? a F M 1 .l a" a4 j fl' j 16' I 30 P 1953 H. MACKIE 2,650,605

PRESSURE REGULATIING DEVICE Filed Nov. 8, 1948 2 She'ets-Shqet 2 Patented Sept. 1, 1 953 UNITED STATES PATENT OFFICE Application November 8, 1948, Serial No. 58,923 In Great Britain November 18, 1947 3 Claims.

This invention relates to pressure regulating devices for use in hydraulic or pneumatic systems, said devices being of the kind comprising a member which, when the fluid pressure fed to the system by a pumpor compressor reaches a pre-determined value, moves to permit said fluid to escape to a tank or to atmosphere. This type of device enables the pump to idle when members of the system are not required to work or to work only under light load and consequently lengthens-the life of the pump.

In this known type of device it has been proposed to provide a piston with two valves, one at each end of the piston rod which passes through the piston, which piston slides in a cylinder bore and is subjected to the action of a spring which surrounds the piston rod so that the valves are alternately moved to close two orifices controlling the supply and exhaust ports of the cylinder.

One object of the present invention is to provide an improved form and construction of a pressure regulating device of the above type which will be relatively simple and capable of maintaining the pressure in an hydraulic or pneumatic system within predetermined limits, another object being to provide apressure regulating device which is easy to adjust without dismantling.

A pressure regulating device of the type decribed according to the present invention comprises a piston, having two valves, one at each end of said piston, which is arranged to reciprocate within a cylinder and is subjected to bias so that the valves alternately close two orifices in said cylinder, a housing adjustable axially with respect to the cylinder and a sup-port adjustable axially in said housing, the support providing a bearing for the biassing means.

The means for imparting bias to the piston may comprise one or more springs, whilst the axial adjustment of the housing and support is preferably attained by screw-threaded connections, one between the housing and the cylinder and one between the housing and the support.

The invention is diagrammatically illustrated in the accompanying drawings in which Figure 1 shows one form and Figure 2 a modified form to a larger scale, like part being given like reference numbers.

Referring to Figure 1 the pressure system comprises a pump I which is connected by a pipe line 3 with a fluid tank or reservoir 2 and is arranged to deliver fluid into the system through lines 4, 5, 6 and l and a non-return valve 8 on 2 the delivery side of Which is a branch line 9 lead ing to a pressure accumulator i0; also on the de livery side of said valve 8 is a connection H of a pressure regulating device. The said device comprises a cylinder or body 12 in the bore it of which is adapted to reciprocate a piston is, the major portion of the length of which is of reduced diameter, leaving two portions i5, one at either end of the full diameter of the cylinder bore. The piston carries at each end a valve is, il and is ported in both flanged extremities as at i8, iii. In threaded engagement with the cylinder l2 and arranged to enter the bore l3 thereof behind the piston i4 is a housing 28 which is internally threaded to receive adjustably a spring support 2!. This support 2! forms a bearing for one end of a coiled spring 22, the other end of ;which is adapted to bear against a spindle 23 forming part of, or in engagement with, the valve ii, the spindle 23 passing through the inner end of the spring housing 20, the spindle being cylindrical and provided with milled flats to allow the passage of fluid through the bore or passage 24 in the spring housing through which the spindle passes. The housing is also provided with ports 25 which communicate with the outlet 20 from the cylinder which is connected by line 2'5 to the fluid tank 2. It will be appreciated that adjustment of the spring action on the piston It can be obtained by relative axial movement between the cylinder l2 and housing 28 and also between the housing 20 and spring support 2!. In that portion of the cylinder If; in which the piston l4 recipr-ccates, which may be called a valve chamber, is a bore 28, at right angles to the axis of the piston, in which bore a plunger 29 is provided which is in mechanical connection with a icy-pass lock valve 36 arranged in a by-pass chamber or passage in the body I2 to which there are connected a branch pipe 3i from the pump connection 4, 5 to the non-return valve 8 and a branch pipe 32 which passes back to the fluid tank 2.

Means such as a locking screw 33 is preferably provided for locking the housing and spring sup port to the cylinder body. Said means may, however, oomprise any other known locking device, for example, the locking device shown and described in British Patent 547,634, of September 4, 1942.

The system works as follows:

Fluid under pressure from the pump I passes through the non-return valve 8 into the system to do the required work, the accumulator l0 acting as a pressure equaliser in known manner.

Due to the bias urged on the piston 14 by the spring 22, the piston is moved so that the valve l6 controlling the supply of fluid to the pressure regulating device is closed until a predetermined pressure is reached. If this pre-determined pressure is exceeded, fluid pressure will force the valve I6 off its seating and move the piston I4 against the spring bias so that the pressure fluid enters the bore I3 of the cylinder and acts on the larger area of the piston allowing a small amount to pass through the ports [8, IS in the piston, so that the valve I! on the other end of the piston is pressed onto its seating. Any fluid which, before closing of the valve ll, exists in the housing is returned through the ports therein, via the cylinder outlet 25 and pipe line 21 to the tank 2 or to atmosphere if the system is pneumatically functioning. At the same time the fluid pressure existing in the cylinder will move the plunger 29 to open the lock valve 39 so that fluid will now pass from the pump mainly into the branch line 32 and back to the tank 2. The system is thus relieved from excess fluid pressure when it exceeds a predetermined value. Should the pressure of the fluid in the system fall below another pre-determined pressure the spring bias on the piston l4 comes into play to close the valve Hi and out the supply of fluid to the cylinder of the pressure regulating device and fluid i again delivered into the system through the normal lines. The value of the pressure for the cutout and cut-in of the pressure regulating device can be Dre-determined by the areas of the valve seats of the valves [6, II, or by altering the characteristics of the bi-assing spring. During all these operations the accumulator ID will tend to equalise the rise or fall of pressure.

It will be appreciated that the travel of the piston l4 and therefore the valves [6, I7, carried thereby, can be adjusted in two ways, that is to say by axial movement of the spring support 2! within the housing 20, and by axial movement of the housing 23 in the cylinder l2 both of which adjustments can be made externally of the pressure regulating device; thus a highly sensitive pressure regulating device is obtained.

It will further be appreciated that as only a part of the fluid under pressure passes through the pressure regulating device as distinct from the whole of the pressure fluid as in known valve arrangements, the device according to the present invention can be small in size and light in weight.

Another form of the invention is illustrated in Figure 2 in which parts similar to those in Figure 1 are indicated by the same reference numeral.

In this arrangement, the cylinder l2 has a fluid connection at 34 communicating with the pump I, which connection leads through an aperture 35 to the pipe 6 and non-return valve 8 and to the lock or bypass valve indicated generally at 38. This valve comprises a valve sleeve 36 with its sealing ring 37 held in position by a spring support 39 which is retained by a nut 40, the support forming a bearing for a spring 38. In the bore of the sleeve 36 and spring support 39- slides the valve 4| which is biassed to the closed position by the spring 38, the valve bein formed with a shoulder 42.

The system works as follows:

Fluid under pressure coming from pump I passes through the lines 4 and 5 into the connection 34, then through aperture 35, the non- '4 return valve 8, into an aperture 43 and through the connection H and pipe line 2' into the system. Fluid pressure will act on the shoulder 42 of the valve 4| but will not be able to move the valve against the force of its spring due to the small area it acts upon. Pressure fluid will be able to pass through aperture 43 into the cut out valve part of the body and act on the valve 16 in a similar way as described in connection with Figure 1. If a predetermined fluid pressure is exceeded, fluid will pass through bore 13 into bore 28 and act on the plunger 29 moving it upwards and carrying the valve 4| with it. Fluid under pressure entering aperture 35 will now pass the valve 4| into connection 26 and return by the pipe line 21 into tank 2, and the drop in the pressure will close the non-return valve 8. After a pre-determined fall in pressure, the force of the spring 22 will return the valve 16 onto its seat. When this valve is thus held on its seat, the force of spring 38 will be able to move the valve M onto its seat, carrying the plunger 29 with it.

The plunger 29 instead of acting directly on the lock valve 30 could be employed to operate any other known means of relieving the fluid pressure, for example a clutch to declutch the pump, or a switch to interrupt the electric current to an electric motor driving the pump. In this latter case the plunger may be arranged in mechanical connection with one or more switches to allow the making or breaking of electrical contacts when the pressure in the system exceeds or drops below a predetermined value.

It will also be appreciated that the provision of a plunger is not essential, since fluid pressure in the bore 28 can be utilised to operate the lock valve directly. Again, if a plunger be used it can be arranged to operate the lock valve and an electric switch simultaneously.

What I claim is:

1. A pressure regulating device of the character described comprising a cylinder having a bore, a valve chamber in said bore, a piston reoiprocable in said chamber, a first valve seat in one end of said chamber, a first valve element carried by said piston and cooperable with said first valve seat, a first passage for conducting fluid under pressure to said first valve seat, a second valve seat in the opposite end of said chamber, a second valve element carried by said piston and cooperable with said second valve seat, a second passage for the escape of fluid from said chamber past said second valve seat, said valve elements being alternatively movable to seated position by movement of said piston, a third passage communicating with said chamber intermediate said valve seats for passing fluid to and from pressure operative means, said pressure operative means being operatively connected to a lock valve controlling discharge of pressure fluid through a by-pass chamber to an exhaust line and comprising a plunger responsive to pressure in said third passage for opening said lock valve, a housing axially adjustable in said bore and carrying said second valve seat, said housing having means therein for biasing said piston to normally maintain said first valve element seated and said second valve element unseated, and a support for said biasing means mounted in said housing, said support being axially adjustable in said hoursing, and said housing and support together sealing said bore.

2. A pressure regulating device of the character described comprising a cylinder having a bore, a valve chamber in said bore, a piston reciprocable in said chamber and having spaced annular end flanges slidably engaging the walls of said chamber, a first valve seat in one end of said chamber, a first valve element carried by said piston and cooperable with said first valve seat, a first passage fer conducting fluid under pressure to said first valve seat, a second valve seat in the opposite end of said chamber, a second valve element carried by said piston and cooperable with said second valve seat, a second passage for the escape of fluid from said chamber past said second valve seat, said valve elements being alter natively movable to seated position by movement of said piston, a third passage communicating with said chamber intermediate said valve seats for passing fluid to and from pressure operative means, said piston having means permitting only restricted communication between said third passage and that one of said first and second passages which is not closed by one of said valve elements, a housing axially adjustable in said bore and carrying said second valve seat, said housing having means therein for biasing said piston 6 to normally maintain said first valve element seated and said second valve element unseated, and a support for said biasin means mounted in said housing, said support bein axially adjustable in said housing, and said housing and support together sealing said bore.

3. A device as claimed in claim 2 in which said piston is provided with a port through each of said end flanges to permit said restricted communication.

HARRY MACKIE.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,003,848 Wood Sept. 19, 1911 1,138,278 Castle May 4, 1915 1,682,848 Moody Sept. 4, 1928 1,771,879 Dowd July 29, 1930 2,191,726 Peters Feb. 27, 1940 2,447,820 Schultz Aug. 24, 1948 2,474,122 Schneck June 21, 1949 

